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A multi-planar volumetric display. ID696143
Introduction
Volumetric displays can be considered to be the most realistic three-dimensional
displays. In these displays real three-dimensional objects can be drawn in a
certain volume. In general, volumetric displays can be devised in two classes. Firstly,
there are displays that are able to generate a pixel at an arbitrary position in some
volume. For instance, such a display might consist of a transparent crystal in
which by means of up-conversion light is generated.
Secondly, a volumetric display can be created by generating several planes
behind each other. An example of such a display uses a stack of switchable diffusers
to generate a "moving projection plane". Subsequently different planes are brought
into a scattering state while the remainder of the planes are translucent. At the same
time, the video content of the fast projector is adapted to the scattering plane.
Information that needs to be drawn between two planes can be approximated by
distribution of the information on the two neighboring planes. If the distance between
the planes is sufficiently small the human brain tends to think that there is a
continuous depth, while in practice it consists of discrete planes only. Switchable
diffusers however are expensive components and a fast projector is not commercially
available.
A promising kind of display that creates several planes uses a stack of semi-
transparent mirrors to create several planes, such that information that lies between
two different planes can be distributed, suggesting a continuous depth. Such a
volumetric display has e.g. a binary tree-like structure of semi-transparent mirrors,
1,2,3,4 (Figure 1). In the example of Figure 1 four pictures a,b,c,d, are provided, that
correspond to four different planes respectively. The display has a small tilt-angle
alpha, with respect to the semi-transparent mirrors, such that there is a path difference
for the light coming from the four pictures. The tilt-angle determines the distance
between the planes. If this angle is zero the distance from all four pictures
to the viewer is essentially the same. In alternat...
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